The long range objectives of this research project are to investigate the toxicity, pharmacological properties, and metabolic disposition of organometallic derivatives of chromium, manganeses, and iron. Particular emphasis is placed on aromatic pi-complexes of Cr(CO)3, ferrocene, and MMT (methylcyclopentadienylmanganese-tricarbonyl). The proposed work includes the synthesis of radioactively labeled MMT, the evaluation of its toxicity in rats using histological and biochemical techniques, and the isolated of metabolites (if any) produced enzymatically from MMT in vivo.